The concordance of signals based on irregular incremental lines in the human tooth cementum with documented pregnancies: Results from a systematic approach

Background and objective There is evidence from previous studies that pregnancies and diseases are recorded in the tooth cementum. This study aims to assess the degree of concordance between signals based on irregular incremental lines (ILs) and reported pregnancies. Material and methods 23 recent and 24 archaeological human teeth with known birth history were included in this investigation. 129 histological sections of tooth roots were assessed for irregularities in appearance and width using a standardized protocol. Similarity of observed irregularities at the section level allowed us to define signals at the tooth level. The sensitivity of signals to detect pregnancies was determined and related to the signal prevalence. Results Pregnancy signals were frequently visually observed. However, applying a standardized process we could only reach signal sensitivities to identify pregnancies up to 20 percentage points above chance level. Conclusions Based on a standardized and reproducible method it could be confirmed that some pregnancies leave visible signals in the tooth cementum. The results show the potential of the tooth cementum to support reconstruction of life courses in paleopathology. However, it seems that not all pregnancies affect the cementogenesis in such a way that irregular ILs are identifiable. Further research is needed to better understand which type of pregnancies and other conditions are recorded in the tooth cementum.

Documented pregnancy, abortion and one other life event -Childbirth: 10.11.1863 (illegitimate pregnancy). The pregnancy was documented in the following court records in the state archives (StABS Gerichtsarchiv U 156, 7.6.1862-13.6.1864, Ehegerichtsprotokoll vom 06.07.1863). The childbirth was documented in the baptismal-and birth register archived in the state archives (StABS Spital AA 1.4 Geburts-und Taufregister 1842-1876). -Abortion (4 th month of pregnancy): 19.07.1865 (illegitimate pregnancy). The pregnancy and abortion were documented in the medical record in the state archives (StABS Spital V 30.27,Fol. 726). -Death of Rosina Drüssel's mother Anna Elisabeth Wullschlegel: 02.12.1845. The death is documented in the death register (Billeter-Sammlung, GHGRB Basel,unter Trüssel,Sumiswald,p. 7). This type of event is not considered in the overall research, however it is captured in the manual signal assessment.

Interpretation
Overall, this example shows a good overlap between signals and documented life history events. Signal 2 is clearly visible corresponding with the pregnancy in the 30 st year of life. The pregnancy which ended in an abortion in the 4 th month of pregnancy before the patient died, did not leave an observable signal. The last ILs at the outer cementum border have usually a lower quality (Mani-Caplazi et al., 2019) and irregularities are more difficult to identify at the border. This may explain why this abortion has not been captured as signal. Another

Z_131 Section 3
interesting observation is that signal 1a coincides with the death of the mother in the 12 th year of life. This is an example that other life events may influence the cementogenesis. The Incremental line (IL) width growth curves have been included to illustrate the across sections signal identification with the two signals 1 and 2 clearly visible across sections.

Z_436 Section 2 Interpretation
The tooth cementum is heterogenous with several signals and sub-signals which partially show a good concordance with documented pregnancies. However, signal allocation to the corresponding pregnancies is not straight forward. Signal 2, 3a and 3b show a relatively good concordance with documented pregnancies. Signal 3a and 3b, 4 and 5a and 5a and 5b show an overlap in signal ILs (see table), which make an allocation to pregnancies more challenging. Signal 4, 5a and 5b show a less clear concordance with documented pregnancies and some allocations to pregnancies are debatable. Pregnancy in the 29 th year of life seems not to be covered by a signal. As in this tooth the total number of ILs varied substantially across the sections, we investigating also the similarity across sections based on a reverse numbering. This starts with the last IL of the original numbering in the IL width growth curves (see Fig. S3 e). As expected, this shows narrower signals near the outer border and a better overlap of pregnancy signal -1a corresponding to signal 5b in the original numbering with the last pregnancy. But, also here an overlap in several signals is present. Overall, it seems many close pregnancies make a precise allocation more difficult in particular with increasing IL numbers. One signal in IL 2 corresponding to an age of 12 may represent another type of event and shows that other influences may have impact on the cementogenesis.

Case PRG028 (recent tooth)
Date of birth of the woman and date of extraction were taken from the medical records of dental clinics and practices in Rostock, Germany. The woman was directly asked about the number of births (including stillbirths and abortions) and the corresponding dates (Künzie und Wittwer-Backofen, 2008

Interpretation
This example shows a good overlap of the pregnancy signal and the reported childbirth but only a moderate overlap between IL numbers of signals and the ILs where the pregnancy signals of the abortions are expected. However, looking at the pattern (the ILs between the signals) the signals align well with the abortions. Kagerer and Grupe (2001) have identified that abortions also leave qualitative markers in the tooth cementum. It is visible that the later signal 4 is covering a wider IL range. Here the alignment across sections is more challenging. The IL width growth curves have been included to illustrate the across sections signal identification with four clearly visible across sections signals. There are no life events documented which explain signal1 and signal 4 and this leaves the question as to what events other than pregnancies leave traces in the tooth cementum.

Case PRG058 (recent tooth)
This case illustrates a weaker overlap of signals and reported pregnancies.
Date of birth of the woman and date of extraction were taken from the medical records of the dental clinic in Germany. The woman was directly asked about the number of births (including stillbirths and abortions) and the corresponding dates (Künzie und Wittwer-Backofen, 2008).

Interpretation
We found that in some cases with no reported pregnancy the cementum shows a relative homogenous structure with signals only in the adolescence (Fig. S3 i). An interesting observation is that signal 3 coincides with the death of her father in the 17 th year of life.